1. Field of the Invention
The present invention relates generally to multiple cassette tape storage libraries with random access cartridge handling. More particularly, the invention provides a compact footprint x-y translation mechanism for transport of a cassette handling elevator for movement of cassettes between multiple storage magazines and one or more tape drive units.
2. Description of Related Art
Magnetic tape storage libraries employed for off-line storage of data for archival or short term backup predominantly employ single reel tape cartridges such as the Model 3480 tape cartridge developed by IBM corporation or the Quantum/Digital DLT cartridge. Operation of the IBM 3480 tape cartridge is disclosed in U.S. Pat. No. 4,452,406. The DLT cartridge employs similar functional characteristics in a case having slightly smaller width and length dimensions than the 3480 cartridge. Each cartridge includes a single reel containing a quantity of magnetic tape stored in a substantially rectangular enclosure with an aperture on one major face to receive a rotating capstan for the tape reel. An aperture in one corner of the cartridge allows access to the free end of the tape web by the tape transport unit.
Individual tape transport units are well known in the industry and the development of tape libraries was accomplished to allow automatic retrieval of cartridges for insertion into one or more tape transport units. Initial tape libraries employed vertical arrays of tape cartridges which could be sequentially dropped into a loading position for introduction into an associated tape transport unit. After use, each tape cartridge was then ejected from the tape transport unit and received in a collection area. However, such approaches lacked random access capability. Storage devices employing magazines capable of accepting an array of tape cartridges were developed with vertical movement of the cartridges relative to a stationary tape transport unit employed for positioning selected tape cartridges. These devices typically require significant vertical space to provide magazine actuation travel.
True random access capability has been provided through tape storage libraries employing magazines having vertically stacked cartridges accessible by an elevator retrieval mechanism which transports cartridges to and from the magazine and tape drive unit. Exemplary of this type of storage library is the Philips Laser Magnetic Storage Division (LMS) "Cartridge Stacker Loader" (CSL).
It is desirable to provide multiple magazine capability for increased cartridge storage while maintaining minimal height and footprint for the tape storage library. While tape storage libraries employing multiple access retrieval mechanisms for separate vertical stacks of cartridges are in commercial development. Such devices typically require non-standard footprint sizes due to mechanical operating constraints. It is therefore desirable to provide a multiple magazine tape storage library employing a multiple access retrieval system capable of supplying cartridges to multiple tape transport units on a random access basis while maintaining a footprint suitable for mounting in conventional equipment rack dimensions.
The use of multiple magazines provides additional complexity in inventorying of cartridges stored in the library. It is desirable that cassettes be individually removable from the magazines without magazine removal and that magazines be removable for group handling of cartridges. To obtain configuration control of cartridges stored in the library, it is therefore desirable that the tape library incorporate a separate cartridge insertion and removal port or mailbox to allow automated positioning of cartridges by the tape library system. Additionally, sensing of general access to the magazines and individual magazine removal or replacement or individual cartridge removal or replacement from a magazine is desirable for recovering configuration control when the mailbox is not employed.
Cartridge retaining mechanisms on magazines employed within the tape library must allow access to and removal of the cartridge from the front of the magazine by an operator/user and from the rear of the magazine by the cartridge manipulation mechanism. Pass-through retaining mechanisms such as that employed in the Philips LMS CSL tape storage library have demonstrated satisfactory performance. However, it is desirable to provide the capability for release of the retention mechanism which is self-aligning and can tolerate dimensional variation imposed by operation of the cartridge retrieval mechanism.